[EKS Workshop] Integrate Spot Managed Nodegroups

[ruecarlo]

Given that EKS now provides spot managed node groups functionality https://docs.aws.amazon.com/eks/latest/userguide/managed-node-groups.html , that has been also released in eksctl most recent version eksctl 0.33.0 the EKS workshop should be updated to support spot best practices, recommending EKS spot managed node groups and moving self-managed node groups per haps to an optional section or as an optional exercise that includes the setup of the aws-notification-handler project as well.

[ruecarlo]

it's already there an included in #141